Time and wavelength division multiaccess with acoustooptic tunable filters

In this article we propose a novel time and wavelength division multiple access (T/WDMA) scheme for a metropolitan area network based on a passive optical star. This scheme supports circuit-switched traffic in an environment with a large number of users with applications that span a broad range of data rates (from voice to full motion video). The scheme can be implemented using acoustooptic tunable filters characterized by a relatively large tuning range (around 100 wavelengths) and a relatively low tuning speed (around 10 μs). Performance of this scheme is studied by simulation for the uniform, single-rate, point-to-point traffic case. We also show how the multiwavelength filtering capability of acoustooptic tunable filters can be used to improve the performance of the proposed T/WDMA scheme.     

Acrolein-sequestering ability of endogenous dipeptides: characterization of carnosine and homocarnosine/acrolein adducts by electrospray ionization tandem mass spectrometry

Acrolein (ACR), the carbonyl toxin produced by lipid peroxidation, is significantly increased in Alzheimer's disease brain. Since ACR is one of the most reactive and neurotoxic aldehydes, and human brain contains both carnosine (beta-alanine-L-histidine) and homocarnosine (gamma-aminobutyryl-L-histidine), the aim of this work was first to evaluate the quenching ability of the two peptides towards ACR and then to characterize their reaction products by electrospray ionization tandem mass spectrometry (ESI-MS/MS; infusion experiments; positive-ion mode). The reaction progress of ACR with carnosine or homocarnosine was studied in phosphate buffer, by monitoring ACR consumption (by reverse-phase LC) and formation of the reaction products by ESI-MS/MS at different incubation times. N-Acetylcarnosine was used as reference compound to identify the sites of reaction. Both the dipeptides were able to quench ACR by almost 60% at 1 h and by more than 85% after 3 h incubation. Different reaction products between ACR and carnosine/homocarnosine were detected after 3 and 24 h, to indicate a complex reaction pathway involving sequential addition of 1, 2 and 3 moles of ACR/mole of the dipeptide to both the beta-alanine and histidine residues. The ESI mass spectra of ACR/carnosine reaction mixtures indicate formation of several molecular species, among which the predominant are: (a) the 14-membered macrocyclic derivatives, deriving from the formation of the iminic bond between the terminal amino group followed by intramolecular Michael addition of the C(3) of the ACR moiety to histidine; (b) the N(beta)-(3-formyl-3,4-dehydropiperidino) derivatives arising from the Michael addition of two acrolein molecules to the amino group of beta-alanine, followed by an aldol condensation and dehydration.The reaction of homocarnosine with ACR follows the same pathway, giving rise to the formation of homologous adducts. The results of this study shed light on the mechanism, until now never demonstrated, through which carnosine and homocarnosine detoxify the highly reactive aldehyde acrolein in a buffer system, and represent the starting point for further studies aimed at elucidating the biological role of these dipeptides in brain.     

Recent advances in the assessment of the antioxidant capacity of pharmaceutical drugs: from in vitro to in vivo evidence

In this review, some well-established assays and more recent markers developed for the understanding of the biological activity of pharmaceutical drugs belonging to different pharmacological classes (nonsteroidal anti-inflammatory drugs, cardiovascular drugs, and central-nervous-system-acting drugs) are considered. The results of in vitro studies are reviewed and critically compared with those available from clinical trials, and their relevance for the elucidation of the mechanism of action of the drugs is discussed. Although from this examination a positive correlation between the in vitro and in vivo data seems to emerge, the small number of clinical trials available, their low number of patients enrolled, and sometimes the arbitrary or inappropriate choice of the biomarker(s) used highlight the need for (1) more standardized protocols to allow a reliable comparison of the results from different studies and (2) the development of new and more appropriate and specific biomarkers for the evaluation of oxidative stress before and after drug intervention.     

Structure elucidation and NMR assignments of two new pyrrolidinyl quinoline alkaloids from chestnut honey

The complete ¹H, ¹³C and ¹⁵N NMR spectral assignments of two new alkaloids isolated from chestnut honey and structurally related to kynurenic acid have been made using 1‐D and 2‐D NMR techniques, including COSY, HMQC and HMBC experiments. The new compounds have been identified as 3‐(2′‐pyrrolidinyl)‐kynurenic acid and its γ‐lactam derivative. Copyright © 2009 John Wiley & Sons, Ltd.     

Almost compactness in fuzzy topological spaces

We introduce and study almost compactness for fuzzy topological spaces. We show that the almost continuous image of an almost compact fuzzy topological space is almost compact. Moreover, we show that generally almost compactness for fuzzy topological spaces is not product-invariant, but if X and Y are almost fuzzy topological spaces and X is product related to Y, then their fuzzy topological product is almost compact.     

Handling the valuation of the predicates in a fuzzy model

Given a fuzzy model, and therefore a graded valuation of the predicates, several handlings of such a valuation are possible. For example, we can change the set of truth values, modify the scale, cut the predicates, and identify truth values. In this exploratory paper we analyze some of the properties preserved under these handlings. To do this we refer to an approach to fuzzy semantics in which the valuation structures can vary freely inside a given type.     

Construction and use of a library of bona fide heparins employing 1H NMR and multivariate analysis

In contrast to most pharmaceutical agents, the major anticoagulant agent, heparin, lacks a uniquely defined chemical structure. It is an inherently structurally varying, poly-disperse polymer, rendering quality control problematic. Structural modifications introduced during manufacture and the presence of possible contaminants are dangers. The comparison of any heparin test sample to a library of bona fide, but intrinsically variable heparins, is limited fundamentally to measuring the degree of similarity between them. A general approach for constructing a suitable illustrative heparin library employing (1)H NMR and multivariate analysis, is proposed and examples shown. Heparin samples contaminated with non-N-acetylated, persulfated, non-glycosaminoglycan carbohydrates (10%) were detected, some of which would not be easily detected under current regulatory guidelines. The ability to identify contaminated heparin is fundamentally dependent on the contents of the library, which should contain all the 'normal' variability within 'heparin'. Oversulfated chondroitin sulfate can be detected (～5%) (using components 1 and 2, but is detectable at 3% using additional components, e.g. 1 and 5) analysing the full spectrum and at <1% if only the N-acetyl region is used. Signals arising from oxidation during the manufacturing processes can also be found. The design, properties and limitations of this approach are discussed. Assembly of such a library of market heparin can be termed the 'Current Statistical Definition of Heparin' (CSDH) and will form the basis of future quantitative methods.     

Abelian <Emphasis Type="Italic">ℓ</Emphasis>-Groups with Strong Unit and Perfect MV-Algebras

We investigate the class of abelian ℓ-groups with strong unit corresponding to perfect MV-algebras via the Γ functor, showing that this is a universal subclass of the class of all abelian ℓ-groups with strong unit and describing the formulas that axiomatize it. We further describe results for classes of abelian ℓ-groups with strong unit corresponding to local MV-algebras with finite rank.     

Fuzzy logic, continuity and effectiveness

 It is shown the complete equivalence between the theory of continuous (enumeration) fuzzy closure operators and the theory of (effective) fuzzy deduction systems in Hilbert style. Moreover, it is proven that any truth-functional semantics whose connectives are interpreted in [0,1] by continuous functions is axiomatizable by a fuzzy deduction system (but not by an effective fuzzy deduction system, in general). Received: 15 February 2001 / Revised version: 31 May 2001 / Published online: 12 July 2002